In radar microwave imaging of the earth's surface by satellite antennas, a phased array of antennas operating at frequencies in the range of 5-10 GHz form images with very good accuracy. Such antennas and imaging systems are known in the art.
In radar imaging and generally in the field of remote sensing, it is known to use dual frequency and dual polarization transceivers in order to be able to have different sensing characteristics, namely, different qualities of resolution and penetration. In particular, higher frequency X-band signals at 9.6 GHz are known for good resolution whereas C-band signals at 5.3 GHz are more capable of penetrating cloud although the imaging resolution is of lower quality.
A constraint of incorporating dual frequency operation into radar satellite antennas for remote imaging is largely physical space and weight. Lightweight and compact dual frequency radar antennas of good efficiency are not known in the art. U.S. Pat. No. 5,241,321 (Tsao) illustrates a microwave antenna in which a radiating patch is placed over a ground plane having a coupling slot for dual frequency circularly polarized radiation. U.S. Pat. No. 4,097,868 (Borowick) describes an antenna for combined surveillance and foliage penetration radar which operates at both X-band and L-band frequencies by providing L-band stripline dipole antennas on plates perpendicular to a flat plate waveguide slot array including broadwall slots for X-band transmission.